Analgesia

Frage	Antworten
Definition	Pain is the conscious perception of noxious stimuli
Pain is individual and depends on ...	Age - young have lower tolerance, elderly may not express pain as plainly Health status Species variation (prey animals) Breed differences
Advantages of pain	Limits extent of injury Encourages rest and healing Individual leanrs to avoid noxious stimuli in future
Disadvantages of pain	Distressing, may increase recovery time Enhances stress response, increasing catabolism and delaying wound healing Anorexia Impairs respiration resulting in reluctance to cough and mucous retention - pneumonia
Disadvantages of pain 2	Self mutilation Sensitisation of CNS
Recognising pain	What is normal for patient? Changes in personality or attitude Quiet docile becomes aggressive Aggressive animal becomes quiet Vocalisation, behaviour, movements Posture, physiological parameters
Vocalisation	Excessive in dogs Spontaneous in cats thuogh less vocal Growling and hissing on manipulation of painful area
Behavioural	Hyperventilation, Agitation, Reduced grooming Decreased or no appetite Dsiturbance to normal sleep pattern Inappropriate U+/F+ Changes in bowel movements (D+)
Behavioural 2	Aggression/resentment of handling Seek solitude or human reassurance Intereference of woundsite Attempts for escape with aggression Horses - excessive sweating/salivation Rabbits - grinding teeth Changes in facial expression
Movement	Restlessness/reluctance to move Stiffness of limbs, gait change, inability to rise Reluctance to lie down Reduced activity Trembling, shaking, thrashing
Posture	Abnormal posture, guarding/protecting painful area of straining Unresponsive sternal or sitting position with hunched back & head low (Cats) Attempting to rest in abnormal position
Physiological Parameters	Increased heart & resp rate Raised body temp Mydriasis (dilated pupils) Blood biochem elevations - eg glucose, corticosteroid, catecholamine conc
Analgesia is underused	Vets get away with it Pian difficult to assess Ignorance Misconceptions regarding use of analgesic drugs
Analgesia is underused 2	Misuse of drugs act Limited no. of licensed analgesic products Inertia/complacency Reservations about side effects Different attitudes-generation gap
Why treat pain?	Correlation from humans Ethicla reasons, O' expectation Common anaesthetic agents have little or no analgesic effect Optimise recovery/healing times Minimise pain = minimise self-trauma
Types of Pain	Acute pain Chronic pain
Acute pain	Sudden onset, immediately after injury Disappears when injury healed Intensity greatest in 24-72 hours Mild-severe, short duration, quickly resolves with tx
Chronic pain	Prolonged pain - 6 months Sudden or gradual with periods of remission or exacerbation May not be associated with injury Difficult to treat
Types of pain Somatic pain:	Ligaments, tendons, bones Easily localised throbbing/stabbing pain
Types of pain Visceral pain:	Smooth muscle walls (abdomen, cranium, thorax) Difficult to localise Cramping/burning
Types of pain Referred pain:	Experienced from site distant from injury
Types of pain Phantom pain:	Sensation or burning or tingling experienced in absent limb
Types of pain Neuropathic pain:	Abnormal processing of nervous activity resulting from injury to higher centres of brain
Controlling pain	Endorphins Local anaesthetic agents Opioids Non-steroidal anti-inflammatory drugs (NSAIDs) NMDA receptor agonists
Endorphins	Endogenous opiate-like peptides produced naturally in CNS Inhibit production of neurotransmitter substance & conduction of pain impulses Raise pain threshold & produce sedation & euphoria Production stimulated by TENS/acupn
Local anaesthetic	Block all sensory input from affected area Site of injury will determine usefulness Bupivicaine or ropivacaine drugs of choice due to duration or action (not licensed)
Topical - EMLA cream applied prior to catheter placement Local block - multiple injs in LA around area of interest with fine bore needle Local 'splash' block - Irrigating wound with LA prior to closure	Regional block - LA admin around nerve, desensitising whole area it supplies Epidural - LA inj into epidural space between dura mater & periosteum providing desensitisation of all nerves leaving spine from there
Opioids	Partial mu agonists - eg Buprenorphine Less reliable against wide pain type Poor dose/response relationship If ineffective increasing dose often does not increase analgesic effect Difficult to change to alternative
Effects of opioid analgesia	Analgesia, sedation, euphoria (cats), resp depression, cough suppression, nausea, V+, constipation, mydriasis (pupillary dilation)
Opioids	Controlled under Misuse of Drugs Act Similar modes of action, activity varies between receptors - mu, kappa, sigma, delta Full-mu agonists (morphine) most reliable pain relief
Examples of opioids	Morphine, Pethidine, Papaveretum, Methadone, Fentanyl, Etorphine, Buprenorphine, butorphanol
Admin of opioids	iv - not pethidine, i/m - pethidine stings s/c - variable uptake Oral - metabolism affects efficacy Sublingual - technically difficult Rectal - Suppositories Epidural - GA, sterilty, skill needed Transdermal - Fentanyl patches
NSAIDs	Inhibit synthesis or prostaglandins, production of COX Block peripheral sensitisation Long duration of effect Antipyretic No sedation
NSAIDs	Greater effect if given pre-emptively Carprofen, Meloxicam, Tepoxalin Compromise renal blood flow GI ulceration in long term use
NMDA receptor agonists	N-methyl-D-aspartate agonist Ketamine, tiletamine - excellent for somatic/neurological pain, poor for visceral Shot duration of action
NMDA receptor agonists	Increased doses produced increased analgesia but also dissociativeness Excellent analgesic as slow infusion either alone or in combo with morphine/lidocaine (IVFT) Observe for toxicity if lidoc used Synergy with opioids
Objective assessment of pain	Simple scoring system useful for standardising pain assessment Assessment of patient behaviour, general demeanour, appetite, pain response Freq of assessment depends on presenting problem - 2h
Objective assessment of pain	Many pain scales produced with no single accepted method. Tailoring to individual practice needs is important Patients with chronic pain should be assessed every 3m or when meds ineffective
Scoring System	0 = no pain, signs of discomfort, resentment to firm pressure 1 = some pain, no discomfort, resentment to firm pressure 2 = mod pain, some discomfort, made worse by firm pressure 3 = severe pain, overt signs of persistent discomfort, made worse by firm pressure

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